A leaked US defence document, reported by the Washington Post, showed the CIA had been tipped off by an allied European agency in June 2022, three months before the attack, that six members of Ukraine’s special operations forces were going to rent a boat and use a submersible vehicle to dive to the seabed using oxygen and helium for breathing, in order to sabotage the pipeline. But the leaked US document said the planned operation had been put on hold.
And, of course, that's not the point of the article in the slightest. It's that two additional explosions were identified on top of the one original one.